Epstein-Barr virus (EBV) is a human gamma herpesvirus that infects most people by adulthood. Infection is associated with infectious mononucleosis, Burkitt's and non-Hodgkin's lymphomas, Hodgkin's disease, nasopharyngeal carcinoma, oral hairy leukoplakia, and some gastric carcinomas. The long-term goals of this research are (i) to elucidate mechanisms controlling latency versus lytic replication of EBV, and (ii) to apply this knowledge toward the development of new therapies for treating some EBV-associated diseases. Dr. Mertz and her colleagues have recently identified a novel cis-acting element, ZV, and its trans-acting factor, ZEB1, that play central roles in regulating EBV's latent-lytic switch gene, BZLF1, during latency and its reactivation by inducers such as TGF-beta and anti-immunoglobulins. The specific aims are the following: (i) Determine importance of ZEB1 in regulating EBV's life cycle via binding the ZV element in the BZLF1 promoter by (a) determining effects of mutations in the ZV element on establishment of latency and reactivation to lytic replication, (b) confirming ZEB1 regulates expression of the BZLF1 promoter via binding the ZV element, (c) determining the effects of ZEB1's abundance on establishment and maintenance of latency and reactivation using cell lines inducible for expression of ZEB1, and (d) looking for correlations between presence of ZEB1 and consequences of infection by EBV by measuring the abundance of ZEB1 mRNA and protein in a variety of human B-lymphocytic and epithelial normal and EBV-associated tumor tissues; and (ii) Elucidate mechanisms by which effectors of cellular signaling pathways induce latency or reactivation of EBV in part via modulating ZEB1 by (a) determining the effects of the EBV-encoded protein LMP1 on ZEB1's abundance, activity, and effects on EBV's life cycle using cells inducible for expression of LMP1 and LMP1 mutants of EBV, and b) testing models for activation of expression of the BZLF1 gene via ZEB1 by looking for correlations between expression and changes in the abundance, cellular localization, DNA-binding activity, co-purifying co-regulators, and post-translational modifications of ZEB1 after activation of cells with anti-immunoglobulins and TGF-beta. These studies should confirm our hypothesis regarding the central roles of ZEB1 and the ZV element in regulating EBV's life cycle and, possibly, lead to novel therapies for immunization against EBV and treatment of some EBV-associated diseases. [unreadable] [unreadable] [unreadable]